<!DOCTYPE html>
<html>
    <meta name="content-type" content="text/html; charset=UTF-8">
    <head>
        <title>Calculator</title>
        
        <!--将按键内容以字符串形式存储在文字框中当按钮为“=”时，调用eval方法计算结果然后将结果输出文字框中-->

<script type="text/javascript">
    var numresult;
    var str;
    
    function onclicknum(nums) {

        str = document.getElementById("nummessege");
        str.value = str.value + nums;

    }

    function onclickclear() {

        str = document.getElementById("nummessege");
        str.value = "";

    }

    function onclickresult() {

        str = document.getElementById("nummessege");
        numresult = eval(str.value);
        str.value = numresult;
        
    }
</script>

    </head>

    <body bgcolor="affff" >
    
    <!--定义按键表格,每个按键对应一个事件触发-->
    
        <table border="1" align="center" bgColor="#bbff77"
            style="height: 350px; width: 270px">
            <tr>
                <td colspan="4">
                    <input type="text" id="nummessege"
                        style="height: 90px; width: 350px; font-size: 50px" />
                </td>
            </tr>
            <tr>
                <td>
                    <input type="button" value="1" id="1" onclick="onclicknum(1)"
                        style="height: 70px; width: 90px; font-size: 35px">
                </td>

                <td>
                    <input type="button" value="2" id="2" onclick="onclicknum(2)"
                        style="height: 70px; width: 90px; font-size: 35px">
                </td>

                <td>
                    <input type="button" value="3" id="3" onclick="onclicknum(3)"
                        style="height: 70px; width: 90px; font-size: 35px">
                </td>

                <td>
                    <input type="button" value="+" id="add" onclick="onclicknum('+')"
                        style="height: 70px; width: 90px; font-size: 35px">
                </td>
            </tr>

            <tr>
                <td>
                    <input type="button" value="4" id="4" onclick="onclicknum(4)"
                        style="height: 70px; width: 90px; font-size: 35px">
                </td>

                <td>
                    <input type="button" value="5" id="5" onclick="onclicknum(5)"
                        style="height: 70px; width: 90px; font-size: 35px">
                </td>

                <td>
                    <input type="button" value="6" id="6" onclick="onclicknum(6)"
                        style="height: 70px; width: 90px; font-size: 35px">
                </td>

                <td>
                    <input type="button" value="-" id="sub" onclick="onclicknum('-')"
                        style="height: 70px; width: 90px; font-size: 35px">
                </td>
            </tr>

            <tr>
                <td>
                    <input type="button" value="7" id="7" onclick="onclicknum(7)"
                        style="height: 70px; width: 90px; font-size: 35px">
                </td>

                <td>
                    <input type="button" value="8" id="8" onclick="onclicknum(8)"
                        style="height: 70px; width: 90px; font-size: 35px">
                </td>

                <td>
                    <input type="button" value="9" id="9" onclick="onclicknum(9)"
                        style="height: 70px; width: 90px; font-size: 35px">
                </td>

                <td>
                    <input type="button" value="*" id="mul" onclick="onclicknum('*')"
                        style="height: 70px; width: 90px; font-size: 35px">
                </td>
            </tr>

            <tr>
                <td colspan="2">
                    <input type="button" value="0" id="0" onclick="onclicknum(0)"
                        style="height: 70px; width: 190px; font-size: 35px">
                </td>
                <td>
                    <input type="button" value="." id="point" onclick="onclicknum('.')"
                        style="height: 70px; width: 90px; font-size: 35px">
                </td>

                <td>
                    <input type="button" value="/" id="division"
                        onclick="onclicknum('/')"
                        style="height: 70px; width: 90px; font-size: 35px">
                </td>
            </tr>

            <tr>

                <td colspan="2">
                    <input type="button" value="Del" id="clear"
                        onclick="onclickclear()"
                        style="height: 70px; width: 190px; font-size: 35px" />
                </td>

                <td colspan="2">
                    <input type="button" value="=" id="result"
                        onclick="onclickresult()"
                        style="height: 70px; width: 190px; font-size: 35px" />
                </td>


            </tr>


        </table>

    </body>
</html>
